Spot Welding between Aluminum Alloy and Low Carbon Steel by Friction Stirring

Abstract

The application of aluminum alloy, which is a typical lightweight material, has been expected to the construction of the transportation vehicle to achieve energy saving by reduction of its weight. However, the structure made of whole aluminum alloy had problems with low strength and high cost. Thus, hybrid structure made of Al alloy and steel is useful because of lightweight and higher strength. To construct the hybrid structure, it is necessary to weld between aluminum alloy and steel. However, the conventional welding methods, like brazing and mechanical fastening, have some problems such as low mechanical strength and low productivity. Also, it is difficult to weld Al alloy and steel by conventional fusion welding. In this study, spot welding between aluminum alloy and low carbon steel by friction stirring was carried out. Especially, optimization in welding conditions was carried out. Moreover, the effect of welding conditions on the joint strength and weld interface was studied. As a result, relatively higher tensile shear strength of the weld which was achieved at an optimum welding conditions was obtained. Temperature near weld interface measured by K type thermocouple during welding was found to be the value lower than the melting point of A5052. From the observation results on microstructure of weld interface, it was found that Fe/Al intermetallic compound layer was formed.